When the hose is cut or if the compressor fails; it creates a pressure differential on the body of roughly 120 Pounds per square inch. The average human has about 3000 square inches of surface area. This results in a force of about 37,500 pounds on the body or about 18.75 Tons. Once the water pressure outside his helmet was greater than the air pressure inside, the resulting "pressure gradient force" would try to equalize those pressures.

The dimensions of a diving helmet like the one in the myth is approximately 19"H x 14 1/2"W and with it being somewhat spherical if you calculate the volume to be between the spherical (app. 1596.256 cubic inches or 0.924 cubic feet) and cubical (3994.75 cubic inches or 2.312 cubic feet) volumes to be approximately 2800 cubic inches/ 1.620 cubic feet (spherical volume plus cubical volume divided by 2) and an average person, at 175.5 pounds, occupies approximately 2.695 cubic feet*. So no matter what the divers entire body, as per the myth, could not possibly fit in the helmet anyway! Even if the helmet was cubical with the same dimensions 19 x 14.5 x 14.5 = 3994.75 cubic inches (2.312 cubic feet) the myth is busted with simple math. In order for the diver to have fit in the helmet, of the estimated 1.620 cubic feet, in a worst case scenario he would have to weigh a maximum of approximately 109.650 pounds.

On 21 June, 1914, a hard hat diver named Edward Cossaboom was working on the salvage crew, recovering bodies from the Empress of Ireland, in the St. Lawrence River. He fell off the ship's superstructure in about 80 feet of water. His tender failed to arrest his fall and he came to rest at 140 feet. The rapid increase in water pressure resulted in sufficient pressure differential that he was sucked into his helmet. The divers who recovered his body said it resembled "a jellyfish with a copper mantle and dangling canvas tentacles.